1. Field
The present disclosure relates to a differential pressure water electrolysis system.
2. Description of the Related Art
Typically, hydrogen gas is used as a fuel gas used to perform a power generation reaction in a fuel cell. The above hydrogen is produced by a water electrolyzer, for example. The water electrolyzer uses a solid polymer electrolyte membrane (an ion-exchange membrane) for generating hydrogen (and oxygen) through electrolysis of water.
An electrode catalyst layer is provided on both surfaces of the solid polymer electrolyte membrane such that an electrolyte membrane-electrode structure is configured, and a current collector is disposed on both sides of the electrolyte membrane-electrode structure such that a water electrolysis cell is configured.
In a water electrolyzer in which a plurality of water electrolysis cells are stacked, voltage is applied to both ends in the stacking direction and water is supplied to an anode current collector. Accordingly, water is electrolyzed and hydrogen ions (protons) are generated on the anode side of the electrolyte membrane-electrode structure, the hydrogen ions permeate the solid polymer electrolyte membrane and is transferred to the cathode side, and the hydrogen ions are combined with the electrons in a cathode current collector such that hydrogen is produced. Meanwhile, on the anode side, oxygen that has been generated together with hydrogen is discharged from the water electrolyzer together with surplus water.
As the water electrolyzer, a differential pressure water electrolysis system that, while producing oxygen on the anode side, produces, on the cathode side, hydrogen that has a higher pressure with respect to the pressure of the oxygen by electrolyzing water is employed. Specifically, current collectors are provided on both sides of the solid polymer electrolyte membrane and separators are stacked on the current collectors and, further, a first flow passage that supplies water is formed between one of the current collectors and one of the separators. Furthermore, a second flow passage that obtains hydrogen generated through electrolysis of water and that has a high-pressure that is higher than the normal pressure is formed between the other current collector and the other separator.
In the above type of differential pressure water electrolysis system, when the pressure of the second flow passage having a high-pressure is released, the pressure in the seal groove that is in communication with the second flow passage can be released in a preferable manner, and an electrochemical device disclosed in Japanese Unexamined Patent Application Publication No. 2010-196133 that aims to prevent damage to the electrolyte membrane to the extent possible is known. The above electrochemical device includes a high-pressure fluid manifold that is in communication with the second flow passage and that extends in the stacking direction of the separator.
One of the separators includes a seal groove that encircle the outside of the high-pressure fluid manifold and in which a sealing member is inserted, and an opening portion that communicates the high-pressure fluid manifold and the seal groove to each other. Furthermore, the other separator includes a seal groove that encircle the outside of the second flow passage and in which a sealing member is inserted, and an opening portion that communicates the second flow passage and the seal groove to each other.
Now, when the pressure of the high-pressure fluid manifold is released, the pressure in the seal groove is released in a desirable manner through the opening portion that directly communicates the seal groove and the high-pressure fluid manifold to each other. With the above, it is stated that when releasing pressure, no difference in pressure occurs between the high-pressure fluid manifold and the seal groove and drastic transfer of the high-pressure fluid from the seal groove to the high-pressure fluid manifold and be prevented in a reliable manner.